desktop to wireless router

hie
i have 2 laptops (xp & vista) and both can connect to internet via a g netgear router. i have added a card on my desktop xp but cant connect although it picks up the router. when i enter the key error msg is about 40 or 104 bits needed or 5 or 13 ascii characters. the same key that is working on the laptops.
Also i would like connect these as a network so that i can share files wirelessly please help